Fluid-meter.



I. 0. WILSON.

FLUID METER.

APPLICATION FILED IfAY 2. I9I7.

Patented Sept. 24, 1918.

6 SHEETS-SHEET l.

wffifejsesx WW... ,1

J. C."WILSON. FLUID METER.

APPLICATION FILED MAY 2. I917.

Patented Sept. 24, 1918.

6 SHEETS-SHEET 2- J. C. WILSON.

FLUID METER.

APPLICATION FILED MAY 2. 191,].

,279,626. PatentedSept. 24,1918

' 6 SHEETS-SHEET 3.

J. 0. WILSON.

, FLUID METER 1,279,626. APPLICATION FILED MAY 2. I917. 24:, .I 6SHEETS-SHEET 4.

Mm 055 3E M A/QzQfi/J' 1. 0. WILSON.

FLUID METER.

APPLICATION FILED MAYZ.I9I7- 1,279,626. Patented Sept. 24,1918.

6 SHEETS-SHEET 5.

W556i flew @wfi 1 m l M m L C. WILSON.

FLUID METER. I v KPFLICATION F ILED MAY 2.1917.

Patented Sept. 24, 1918.

6 SHEETS-SHEET 6.

UNITED STATES ATET FICE.

JOHN 0. WILSON, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HAMMERMFG. CO., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

FLUID-METER.

Specification of Letters Patent.

Patented Sept. 24, 1918.

To all whom it may concern:

Be it known that I, JOHN C. 'TILSON, a citizen of the United States,residing at Milwaukee, in the county of Milwaukee and State of\Visconsin, have invented new and useful Improvements in Fluid-Meters,of which the following is a specification.

This invention relates to meters.

It relates particularly to meters for measuring the flow of fluids suchas steam, vapors, gases and the like, although it is not limited to suchuse. 7

Steam and gases often carry appreciable quantities of water or watervapor, the presence of which is due to many causes. The steam or gas maybe saturated with water vapor at the point where it is generated or inthe leaning and cooling processes and as the gas passes through thedistributing system to storage tanks or to points where it is consumed,its ten'iperature decreases with a consequent condensation of some ofthe water vapor to water. This condensed water may be carried alongmechanically with the flowing stream of gas, some of it flowing alongthe inner surface of the conduit through which the as is passing, andsome of it being carrie in suspension in the stream of gas in the formof minute globules of water in the nature of water fog. Moisture may ofcourse be present in the gas due to other causes.

When this wet steam or gas is passed through a meter, the moisturecondenses on the meter parts and interferes with accuracy of the meter.,Errors are thus introduced. The present invention relates to means foreliminating these errors. It is illustrated and described in connectionwith thermal fluid meters, although it is applicable to meters of othertypes.

Thermal fluid meters employ thermal or thermodynamic effects formeasuring the flow of fluids. The specific heat of the fluid beingknown, the flow is measured by determining the effect of heat transferbetween a stream of the fluid and means subject thereto. The meters mayemploy various methods for measuring the flow by thermal effects. Heatmay be imparted to or absorbed from a flowing stream of fluid and thetemperature changes in the fluid observed. The specific heat' of thefluid being known the variations in its temperature are a measure of therate of flow. Any one of the variables involved in such a measurementmay be kept constant and the others measured to determine the rate offlow. The flow may also be measured by determining the cooling effect ofthe flowin fluid on a source of heat subjected to said fluid, or bydetermining the heating effect of said fluid on a cooler body which issubjected to said fluid, all of these methods depending upon heattransfer to or from the fluid.

When the fluid to be measured is wet the moisture tends to interfereWith the simple relations underlying the heat transfer and the effect ofthis transfer and introduces inaccuracies in the meter. When heat isimparted to the fluid, a portion of the heat must be used to vaporizethe moisture before a rise in temperature of the fluid can be produced.Furthermore in some types of meters the calibration is dependent uponthe rate of heat dissipated from the heater, or to the cooler, per unitarea of same. Any moisture on the surface of the heater or the coolerwould affect the rate of heat transfer from or to the surface. Thenagain, moisture tends to hasten corrosion of surfaces in gas atmospheresand therefore the surface condition of the heater or cooler is radicallychanged by any moisture present.

It is accordingly important that means be provided which will insurethat the fluid to be measured is thoroughly dry before it enters themeter. It is further important that means be provided for varying theeffect of the drying means since variations in the rate of flow vary thedemand upon the drying means.

One of the objects of the invention is to provide an improved meterhaving means for drying the fluid before it reaches the meter and meansfor varying the effect of the drying means on the fluid.

Another object is to make thedrying means automatically esponsive to therate of flow of the fluid.

Another object is to provide an improved met-er having means for heatingthe fluid to dry the same before it reaches the meter, the quantity ofenergy supplied to said heating means being automatically regulated inaccordance with the flow of fluid.

Another object is to provide an improved thermal fluid meter havingmeans for automatically drying the fluid entering the meter in responseto the rate of flow of fluid.

Another object is to provide an improved method of measuring the flow offluid.

Other objects and advantages of the invention will hereinafter appear.

The invent-ion is illustrated in the accompanying drawings in which-Figure 1 is a simplified diagrammatic view representing a thermal fluidmeter,

drying means for the fluid and means for automatically varying theeflect of the drying means in accordance with the rate of flow of thefluid.

Fig. 2 is a diagrammatic view of a commercial form of the apparatusshown in Fig. 1.

Fig. 3 is a view similar to Fig. 2 but illustrates a difi'erent mannerof automatically varying the effect of the drying means.

Fig. 1 is a diagrammatic view showing the electric drying coil connected,with the electric heater of the meter in a difl'erent manner from thatshown in Fig. 3.

Fig. 5 is a diagrammatic view of a thermal fluid meter similar to thatshown in Figs. 2 and 3 and illustrates how the effect of a fluid orliquid drying medium may be automatically controlled in accordance withthe rate of flow of the fluid to be measured.

Fig. 6 is a diagrammatic view illustrating the manner in which theeffect of a drying means utilizing products of combustion may beautomatically varied in accordance with the rate of flow of the fluid.

Fig. 7 is a vertical section taken on the line 77 of Fig. 6.

Fig. 8 is a diagrammatic view illustrating means for automaticallyrendering the drying means inoperative when the rate of flow of thefluid is very low, or when the fluid ceases to fiow altogether.

Fig. 9 is a detail view showing in section the fuse plug employed inFig. 8, and

Figs. 10 and 11 are diagrammatic views of electrical drying means havingseveral heating coils and illustrate how the drying effect may be variedby varying the electrical connections between the coils.

The drying means, which will hereinafter be referred "to as thepreheater. is disclosed in combination with a thermal fluid meter of thetype shown in the patent to C. C. Thomas, No. 1,222,492 of April 10,1917 A meter of this type is commonly known as a Thomas meter.

Fig. 1 is a simplified diagram showing a Thomas meter and an electricpreheater for the fluid to be measured, and shows the manner in whichthe current supplied to the preheater may be varied in accordance withthe rate of flow of the fluid.

The meter comprises a heater which is automatically controlled by a pairof thermometer resistances to maintain a predetermined constanttemperature, rise in the fluid. If this be done then the energy consumedby the heater in maintaining this constant temperature rise will be ameasure of the rate of flow of the fluid.

The housing of the meter is shown at 1. It constitutes a conduit throughwhich the fluid to be measured flows in the direction of the arrow. Anelectric heating coil 2 is positioned in the conduit 1 and is connectedacross the supply mains 3 and 4. Current is supplied to the heater 2through a conductor 5, a rheostat arm 6, variable resistance 7 conductor8, and through the current coil 9 of the wattmeter 10. This circuit isrepresented by the heavy lines. The voltage coil 11 of the wattmeter 10is connected in shunt with the heating coil 2 by the conductors 12 and13. When the rheostat arm 6 is actuated to vary the resistance 7 thecurrent supplied to the heating coil 2 is varied, thus varying theamount of heat dissipated from the coil. The Wattmeter 10 measures thewattage consumed by the heater.

Thermometer resistances 14 and 15 whose resistance varies as theirtemperature varies are placed on opposite sides of the heating coil 2.These thermometer resistances are connected at one side to the supplymain 4, and at the other side by means of conductors 16 and 17 to a\Vheatstone bridge. The thermometer resistances 14 and 15 constitute twoarms of the -Wheatstone bridge. The other two arms 21 and 22 of theWheatstone bridge are connected by means of a conductor 23 to the supplymain 3.

A galvanometer 24 is bridged across the resistances of the \Vheatstonebridge by conductors 25 and 26. \Vhen the lVheatstone bridge isunbalanced the needle 27 of the galvanometer will be deflected to oneside or the other.

The WVheatstone bridge is provided with an adjusting resistance 19 inone side and in its opposite side there is provided a resistance 20adapted to be shunted out by means of an ordinary plug switch 20. Theresistance 20 is intended to correspond to the change in resistance ofthermometer resistance 15 due to the predetermined increase oftemperature produced by the heating coil 2. In the adjustment of theWheatstone bridge the bridge is balanced in the ordinary man ner, theplug 20 being first inserted so as to shunt out the resistance 20 andadjusting resistance 19 being ad usted until no, or substantially no,current flows through the conductors 25 and 26, indicating that bothsides of the bridge are in balance. The plug is then removed, at oncethrowing the bridge out of balance and therefore deflecting the needle27; but, as will hereinafter appear, the balance of the bridge will berestored and the needle 27 will be brought back to normal position when,by the action of the heating coil, the resistance of the thermometerresistance 15 has been changed an amount corresponding to theredetermined rise in temperature desired to e maintained.

If the galvanometer needle 27 is deflected to the left in the drawingthe needle will engage a contact 28 and a circuit will then be completedfrom the supply main 3 through a conductor 29 connected to the needle27, through contact 28, conductor 30, elect-ro-magnet 31 and conductor32 to the supply main 4. If the needle 27 is deflected to the right inthe drawing it will engage a contact 33 and a circuit will thenbecompleted through the conductor 29, galvanom eter needle 27, conductor34, electro-magnet 35, and conductor 32 to the supply main 4. The twoelectro-magnets 31 and 35 are con: nected to the rheostat arm 6. \Vhenthe electro-magnet 31 is energized the rheostat arm 6 is moved in onedirection to vary the resistance 7. and when the electro-magnet 35 isenergized the rheostat arm 6 is moved in the opposite direction to varythe resistance 7. The resistance 7 is, therefore, automatically variedin accordance with the deflections of the galvanometer needle 27.

It will now'be seen that the function of the parts above described is tomaintain a constant-difference in resistance between the thermometerresistances, or, in other Words, a constant temperature rise in thefluid be tween the points where the thermometer resistances 14; and 15are located. The thermometer resistance 14 assumes the same temperatureas the incoming fluid and the thermometer resistance 15 assumes thetemperature. of the fluid after it has been heated. 'hen the meter is inoperation the \Vheatstone bridge will be balanced so long as the heater2 is imparting just sufficient heat to the fluid to maintain a constanttemperature rise between the points where the resistances 14 and 15 arelocated. As the rate of flow of the fluid through the meter varies it isobvious that the amount of heat dissipated from the heater will have tobe varied to maintain the constant temperature rise in the fluid. lf therate of flow decreases the fluid will be heated to a greater extent, andthe resistance of the thermometer resistance 1.) relative to theresistance of the thermometer resistance 14. will change. thusunbalancing the lVheatstone bridge. This will the left and cause theelectro-magnet 31 to insert more resistance of the rheostat deflect thegalvanometer needle to in series with the heating coil 2. This willreduce the heating eflect of the heater until the \Vheatstone bridgeagain balances. On the other hand, if the rate of flow of the fluidincreases the fluid will not be heated sufficiently to maintain theconstant temperature rise. A change in the resistance of the thermometerresistance 15 relative to the resistance of the thermometerresistance'lt will then unbalance the \Vheatstone bridge and cause thegalvanometer needle to complete-a circuit through the electro-n'iagnet'35, This will remove some of the resistance 7 from the circuit of theheating coil 2 thus increasing the heating effect of the heater. Theamount of heat dissipated from the heating coil is, therefore,automatically varied to maintain a constant difference between theresistances of thermometer resistances 1t and 15, or, in other words, tomaintain a constant temperature rise of the fluid between the pointswhere these'thermometer resistances are located. The amount of heatrequired to maintain this constant temperature rise is a measure of therate of flow of the fluid. Therefore, by reading the wattmeter 10 andreferring to suitable calibration curves the rate of flow of the fluidmay be determined, or, if desired, the wattmeter 10 may be calibrated toread directly in terms of rate of flow of the fluid.

The housing for the preheater is shown at 36. This housing contains anelectric heating coil 37 which is connected across the mains 3 and 4. Asthe rheostat arm 6 moves it serves to vary resistance 38 connected inseries with the heating coil 37 bymeans of the conductor 39. From theabove description it is obvious that the arm 6 is shifted in accordancewith the variations in the rate of flow of the fluid. Therefore, thcurrent supplied to the coil 37 1S varied in accordance with the rate offlow of the fluid because the arm (3 varies theresistance in series withthe coil 37. As the rate of flow decreases the current supplied to theheating coil 37 is decreased thus reducing the heating effect of thecoil. As the rate of flow of the fiuid increases the current supplied tothe heating coil 37 is increased, thus in creasing the heating effect ofthe coil.

Fig. 2 is a diagrammatic representation of a connnercial form of theapparatus shown in Fig. 1. The underlying principles of operation,however, are exactly the same. In Fig, 2 the current supplied to thepreheater coil 37 is varied by means of a rheostate 40 which correspondsto the rheostat 38 in Fig. 1. The current supplied to the heating coil 2is varied by means of rheostat 41 which corresponds with the rheostat 7in Fig. 1. The rheostat arm 42 of the rheostat 40, and the arm 43 of therheostat 41 are both mounted upon a shaft- H carrying a ratchet wheel45. Two rocker arms 46 and -17 are loosely mounted upon the end of theshaft- 44. These rocker arms are continuously oscillated by means ofconnecting rods 48 connected to a crank 19. The crank 19 is rotated froma motor 50 by suitable reduction gearing. An electro-magnet 51 iscarried by the rocker arm 46 and a similar electro-magnet 52 is carriedby the rocker arm 47. These electro-magnets correspond to theelectro-magnets 31 and 35 of Fig. 1. These magnets serve when energizedto actuate pawls 53. .The pawls 53 are normally out of engagement withthe teeth of the ratchet wheel 45, but when either of the pawls isattracted by its electro-magnet the pawl engages a tooth on the ratchetwheel.

The Vi'heatstone bridge shown in Fig. 2 is substantially the same asthat shown in Fig. 1 and is connected to the thermometer resistances 14and 15 in the'same manner as in Fig. 1. Furthermore. the galvanometer24: is connected across the resistances of the Wheatstone bridge by theconductors 25 and 26 in the same manner as in Fig. 1. The needle 27 ofthe galvanometer is diagrammatically shown in association with thegalvanometer and is represented again just below the vVheatstone bridgeto illustrate how the needle controls the circuits of the electromagnets51 and 52. The needle swings over asupport 54 which carries two contactstrips 55 and 56. These correspond to the contacts 28 and 33 in Fig. 1.The support 54 is reciprocated in a vertical direction by means of aconnecting rod 57 and crank 58. The crank 58 is associated with the endof a shaft 59 which is rotated from the motor 50 by suitable reductiongearing. Just above the needle 27 is a series of contacts arranged intwo groups. Those of the first group are shown at 60 and are .locatedabove the contact strip 55, and those of the second group are shown at61 and are located above the contact strip 56. In the present instancethere are three contacts in each group. The two extreme contacts areconnected by means of a conductor 62 to a finger 63. Likewise the nexttwo contacts are connected by means of a conductor 64 to a finger 65,and two innermost contacts are connected by means of a conductor 66 to afinger 67. The contacts 63, and 67 coiipcrate with contact segments 68,69 and 70 respectively carried by a drum 71 which is mounted upon theshaft 59. The contact segments 68, 69 and 70 are electrically connectedto each other and to a fourth contact segment 72. This segment 72cooperates with a finger 73 which is connected by means of a conductor74 to one of the supply mains. The contact segments 68, 69 and '70 areof successively increasing length for a purpose hereinafter described.

As the drum 71 rotates the support 54 is reciprocated. If the needle 27has been deflected to one side or the other by an unbalancing of the\Vheatstone bridge, it will be clamped. when the support 54 movesupwardly, between one of the contact strips on the support and one ofthe contacts above the support. If the needle is deflected to the leftin the drawing a circuit will be completed through the magnet 51 by thedrum 7], and if the needle is deflected to the right a circuit will becompleted through the magnet 52 by the drum 71. The purpose of thecontacts 60 and 61 and the segments on the drum 71 is to determine thelength of time that the magnets 51 and 52 will be energized. If theneedle 27 is deflected only a small amount to the left it-will beclamped against the innermost contact 60 and then when the drum 71 hasrotated a sufiicient distance to bring the segment 70 under the finger67 a circuit will be completed through the magnet 51, contact strip 55,conductor 66, finger 67, segment 70, segment 72, finger 73 and conductor74. The magnet 51 will be energized until the segment 70 passes fromunder finger 67. The segment 70 is of such length that the magnet willbe energized only long enough to move the ratchet a distance of onetooth. If the needle had been deflected to the right the same amount acircuit would have been completed through the magnet 52 and through thesame segment 70. In this case the ratchet wheel would be rotated adistance of one tooth but in the opposite direction. Likewise if theneedle 27 is clamped under the middle contact 60 or the middle contact61 a circuit will be completed through the contact segment 69 and one ofthe electro-magnets, depending upon in which direction the needleswings. The segment 69 is of such length that the magnet will beenergized long enough to move the ratchet wheel a distance of two teeth.If the needle swings a suilicicnt distance to be clamped under either ofthe extreme contacts 60 or 61 the circuit to one of the magnets will becompleted through the segment 68 which is of such length as to energizethe magnet long enough to move the ratchet wheel 15 a distance of threeteeth. The amount of movement of the ratchet wheel 45 and its directionof movement therefore depend upon the amount of deflection of thegalvanoineter needle and its direction of de flection. The rheostat 41is therefore varied an amount which depends upon the amount ofdeflection of the galvanometer needle.

As therheostat for the preheating coil 37 is actuated from the sameshaft as the rheostat for the heating coil 2 of the meter, it is obviousthat the current supplied to the preheating coil will be automaticallyvaried in accordance with the rate of flow of the fluid. I

In Fig. 3 the rheostat for the preheatin;

coil is omitted and a single rheostat 75 actuated from the shaft 44serves to vary the energy supplied to both the heating coil 2 of themeter and the preheating coil 37. This is accomplished by connecting thepreheating coil 37 in series with the heating coil 2 as shown by theheavy lines. The energy supplied to the preheating coil 37 is thereforeautomatically varied in accordance with the rate of flow of the fluid,because it is connected in series with the heating coil 2 and the energysupplied to the heating coil 2 is varied in accordance with thevariations in the rate of flow of the fluid. The same result may beobtained by connecting the preheating coil 37 in parallel with theheating coil 2. Such an arrangement is shown in Fig. 4. In Fig. 4 thepreheating coil 37 is connected across the heating coil 2 by means ofthe conductors 76 and 77. In Fig. 4 the energy supplied to the heat ingcoil 2 and the preheating coil is controlled by the rheostat 75 in thesame manner as shown in Fig. 3. The only material difference betweenFig. 4 and Fig. 3 is that the preheating coil is connected in parallelwith the heating coil 2 instead of in series therewith.

Obviously the preheater need not be of the electrical type. A steam orhot water coil located in the path of the fluid would serve topreheatand dry the same in the same manner that the electricalpreheating coil 37 dries the fluid.

Fig. 5 illustrates theuse of a preheater having a coil 78 located in thehousing 36.

ot water or steam or any other heated fluid medium may be circulatedthrough this coil. In order to vary the amount of heat dissipated fromthe coil 78 in accordance with the rate of flow of the fluid through theconduit a valve 79 is provided. This valve is connected with the shaft4.4 of the rheostat 7 As the rate of flow of the fluid varies and as theshaft 44 rotates to vary the resistance 75 it is obvious that the valve79 will be actuated to control the flow of heat ing fluid through thecoil 78. The heating fluid supplied to the coil 78 is therefore variedautomatically in accordance with the variations in the rate of flow ofthe fluid.

Figs. 6 and 7 show a gas preheater the housing 80 of which is located inthe gas main just ahead of the meter. In these figures the meter is notshown. A portion of the housing of the preheater forms a heating chamber81 in which there is located a burner 82. The heated air and products ofcombustion pass upwardly through tubes 88 and the fluid to be measuredis caused to flow by these tubes and be heated thereby. The burner 82may be supplied with fuel from any suitable source. lVhen the gas beingmeasured is serviceable as fuel a portion of the gas may be taken fromthe main by a. pipe 84 and supplied tothe burner. A valve 85 whichcorresponds to the valve 79 in Fig. 5 is actuated from the shaft 44 inthe same manner that the valve 79 is actuated in Fig. 5. As the shaft 44is rotated in accordance with the variations of the rate of flow of thefluid to be measured it is obvious that the gas supplied to the burner82 will be varied in accordance with the rate of flow of the fluid andhence the heat supplied by the burner will also be automatically variedin accordance with the rate of flow of the fluid through the conduit.

Fig. 8 discloses means for controlling the supply of energy to thepreheater by rendering the preheater ineffective when the fluid flowsslowly through the conduit or ceases to flow altogether. The housing ofthe preheater is shown at 86 and the preheating coil is shown at 87.Current is supplied to the preheating coil 87 from the mains 88 and 89through an electro-magnetic switch 90 and rheostat 91. In this case therheost-at 91 may be a manually operated rheostat and the energy suppliedto the preheating coil may therefore be varied by hand in accordancewith the rate of flow of the fluid as indicated by the meter. Theelectro-magnet of the switch 90 is normally energized by current passingthrough the circuit indicated by the relatively light lines. Thiscircuit contains a fuse plug 92 which is adapted to be screwed into thetop of the conduit as shown in Figs. 8 and 9 at a point closely adjacentto the preheater. In this figure the conduit is represented in planview. The plug 92 has a fuse ribbon 93 associated therewith throughwhich the current must pass in order to maintain the circuit of theelectromagnetic switch 90 closed. The fuse ribbon 93 is designed to meltat a. predetermined temperature beyond which injury might be done to themeter parts. As the rate of flow of the fluid decreases or if the fluidceases to flow altogether the preheater may heat the fluid to such anextent that the excessive heat may cause injury to various parts of theapparatus such as the parts of the meter,

acking material in joints, etc. However,

' efore this temperature is reached the fuse of the plug 92 melts andbreaks the retaining circuit of the electro-magnetic switch 90 thuscausing this switch to open. When the switch 90 breaks the circuit ofthe preheatng coil is opened thus rendering the preheating coilineffective.

Substantially the same result produced in Fig. 8 may be obtainedin Figs.1 and 2 by making the last one or more contacts of the preheaterrheostat blank contacts as shown at 94-. As the rate of flow decreasesand the shaft H is actuated to insert resistance in series with theheating and preheating coils the arm 6 in the case of Fig. 1 and the arm42 in the case of Fig. 2 will eventuall move the circuit of thepreheating coil.

to the blank contact or contacts 94 and break This is merely aprecautionary measure to prevent the fluid from being excessively heatedwhen the rate of flow of the fluid becomes very low in value.

Figs. 10 and 11 show still another way of varying the effect of thepreheater. In these figures only the housing of the preheater is shownand instead of one preheater coil several coils are employed. In thepresent instance two coils indicated at 95 and 96 are used. Theconductors of these coils may be connected to suitable terminals at anaccessible point outside of the preheater housing where the electricalconnections between the coils 95 and 96 may be changed. Only one coil ofthe preheater may be used, or both may be used and connected either inserles or in parallel. The amount of heat dissipated from the preheaterwill be difi'erent in each case. In Fig. 10 the two coils 95 and 96 areshown connected in parallel, whereas in Fig. 11 they are shown connectedin series. The preheating coils in Figs. 10 and 11 may be connecteddirectly across the supply mains if desired because the change from oneto two coils and from series to parallel connections or vice versa, maysufficiently vary the heating effect of the preheater to take care ofconsiderable changes in the rate of flow of the fluid.

It will now be seen that in all of the figures there is disclosed meansfor controlling the supply of energy to the preheater to vary theheating effect of the preheater when the rate of flow of the fluidchanges. In some instances the preheater is even rendered ineflectivewhen the fluid flows very slowly or'ceases to flow altogether.

Although the preheater and its controlling and regulating means havebeen illustrated in connection with a Thomas meter it will be understoodthat the specific type of meter employed is immaterial to the invention.Furthermore, the exact type of preheater employed is immaterial as isevidenced by the fact that a number of different types of preheaters areherein disclosed.

The invention has been specifically described for illustrative purposesonly and various changes and modifications may be made without departingfrom the scope of the invention as defined by the accompanying claims.

What I claim is:

l. The combination with a fluid meter of means for drying the fluidbefore it enters the meter and means for automatically controlling thedrying means in accordance with the rate of flow of fluid.

2. The combination with a fluid meter of means for supplying heat to astream of fluid entering the meter to dry said fluid before it enters"1e meter and means for tarmac automatically controlling the heatingmeans in accordance with the rate of flow of fluid.

3. The combination with a fluid meter of electrical heating means forsupplying heat to a stream of fluid to dry said fluid be fore it entersthe meter and means for automatically controlling the supply of energyto said electrical heater in accordance with the rate of flow of fluid.

4. The method of measuring the flow of fluids which consists in passinga stream of 1 fluid into heating proximity to a supply of heat,varying'said heat supply in accordance with the rate of flow of fluid todry said fluid, and measuring the flow of the dry fluid.

5. The method of measuring the flow of fluids which consists in passinga stream of fluid into heating proximity to an electrical heating meansto dry the same, varying the energy supply to said heating means inaccordance with the rate of flow of fluid and measuring the flow of dryfluid.

6. The combination with a meter for measuring the flow of fluids bythermal effects of means for drying the fluid before it enters the meterand means for automatically controlling the drying means in accordancewith the rate of flow of fluid.

7. The combination with a fluid meter of means for heating the fluidbefore it enters the meter and means for controlling the heating meansin accordance with the rate of flow of fluid for the purpose of insuringaccuracy of the meter for different rates of flow.

8. The combination with a fluid meter of means for drying the fluidbefore it enters the meter and means for controlling the drying means inaccordance with the rate of flow of fluid for the purpose of insuringaccuracy of the meter for different rates of flow.

9. The combination with a fluid meter of means for heating the fluidbefore it enters the meter and means for changing the rate of supply ofenergy to said heating means when the rate of flow of fluid changes toinsure accuracy of the meter for different rates of flow.

10. The combination with a fluid meter of means for heating the fluidbefore it enters the meter and means for automatically rendering saidheating means ineflective when the rate of flow of the fluid decreasesto a low value.

11. The combination with a fluid meter of means for heating the fluidbefore it enters the meter and means for automatically rendering saidheating means ineflective when the flow of fluid ceases.

12. The combination with a fluid meter of means for heating the fluidbefore it enters the meter and means whereby the heat dissipated fromthe heater may be varied for the purpose of insuring accuracy tive whenthe rate of flow of the fluid deof the meter for different rates of flowof creases to such a value that the heat imthe fluid. parted to thefluid by said first named means 10 13. The combination with a fluidmeter may produce injurious effects. 5 of means for heating the fluidbefore it In witness whereof, I have hereunto subenters the meter, andmeans for aut0mati scribed my name. cally rendering said heating meansineflec- JOHN C. WILSON.

